Ballscrew

ABSTRACT

A ballscrew having a ball re-circulation path within the screwshaft of the ballscrew.

[0001] The present invention relates to a ballscrew.

[0002] Hitherto, ballscrews have been provided with a ball re-circulation path within the ballnut of the ballscrew. The disadvantage of this construction is that the screwshaft needs to be long relative to the ballnut.

[0003] The present invention seeks to provide a remedy.

[0004] Accordingly, the present invention is directed to a ballscrew having a ball re-circulation path within the screwshaft of the ballscrew.

[0005] Preferably, at least a part of the ball re-circulation path is provided by an insert inserted into the screwshaft. In this case, it is advantageous to have an insert which is concentric with the screwshaft.

[0006] Deflectors to direct the balls of the ballscrew into the re-circulation path may be in the form of generally circular or part-circular elongate members which engage the screwshaft. These deflectors may take the general form of circlips.

[0007] An example of a ballscrew made in accordance with the present invention is shown in the accompanying drawings, in which:

[0008]FIG. 1 shows an axial section through such a ballscrew;

[0009]FIG. 2 shows two half cross-sectional views of a screwshaft of a ballscrew shown in FIG. 1;

[0010]FIG. 3 shows a side view of a screwshaft of the ballscrew shown in FIG. 1;

[0011]FIG. 4 shows two half cross-sectional views of a screwshaft of a ballscrew shown in FIG. 1 with deflectors;

[0012]FIG. 5 a side view of a screwshaft of the ballscrew shown in FIG. 1 with deflectors;

[0013]FIG. 6 shows a deflector of the screwshaft shown in FIG. 1, viewing it along a line which passes through the centre of the deflector in a direction generally perpendicular thereto;

[0014]FIG. 7 shows a generally sectional view through an insert located in the screwshaft of the ballscrew shown in FIG. 1; and

[0015]FIG. 8 shows a side view of the insert shown in FIG. 7.

[0016] In FIGS. 1 to 8, there is shown a ballscrew 10 having a screwshaft 12 surrounded by a ballnut 14 so that the screwshaft 12 and the ballnut 14 are concentric with one another, sharing a common axis 16 of the ballscrew 10. Around an outer cylindrical surface 18 of the screwshaft 12, there is provided a helical groove 20. This is in registration with a helical groove 22 formed around the inner cylindrical surface of the ballnut 14 such that the grooves 20 and 22 together define a helical track for balls 24 of the ballscrew 10. Two bores 26 are formed towards the two ends of the groove 20 of the screwshaft 12, these bores 26 slanting inwardly from the groove 20 to the screwshaft interior. Deflectors 28 (shown in FIGS. 4, 5 and 6) are in the form of circlips and can be rotated or snap-fitted into the groove 20 of the screwshaft 12. One end of each circlip 28 has a surface which is on a slant relative to the groove 20 and which is generally flush with an interior surface of the associated bore 26.

[0017] An insert 30 of plastics material is inserted into the screwshaft 12 so as to be coaxial therewith and is formed with a re-circulation path 32 to transfer balls 24 from one end of the groove 20 to the other end thereof via the screwshaft interior.

[0018] It will be noted that the length of the groove 20 around the outside of the screwshaft 12 is substantially shorter than the length of the groove 22 formed around the inside of the ballnut 14.

[0019] Modifications in the illustrated construction may occur to the reader without taking the resulting construction outside the scope of the present invention. For example, instead of circlip-type deflectors, there may be provided small hood-like protuberances extending from the groove 20 of the screwshaft 12 at the positions of the bores 26. 

I claim:
 1. A ballscrew having a ball re-circulation path within the screwshaft of the ballscrew.
 2. A ballscrew according to claim 1 , wherein at least a part of the ball re-circulation path is provided by an insert inserted into the screwshaft.
 3. A ballscrew according to claim 2 , wherein the said insert is concentric with the screwshaft.
 4. A ballscrew according to claim 1 having deflectors to direct the balls of the ballscrew into the re-circulation path, which are in the form of generally circular or part-circular elongate members which engage the screwshaft.
 5. A ballscrew according to claim 4 , wherein the deflectors take the general form of circlips. 